Question:
If I change the DACCLK on the AD9164 when using it as a DDS , what is the recovery time? How fast can I change sample clock and tuning word?
Answer:
The part would need to re-lock the DAC clock DLL and clear out the NCO phase accumulator, which happens in a few hundreds of clock cycles.
The safest method to do this would be to re-run the DAC start up sequence, which would add to the time to switch DAC clock frequency due to the series of SPI writes, but there is probably a subset of things that could be done, like perhaps disabling the DAC clock DLL, then re-enabling it, checking that the DLL re-locked, and then it should be good to go. This hasn't been characterized, but is a method the customer could try.
The speed to change NCO frequency is dependent on the number of SPI register writes and the SPI programming speed. At 100 MHz SPI writes, a single register write can be made in 240 ns, with an approximate 20 ns for the NCO to hop to the new frequency using phase discontinuous switch mode.